/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.state;

import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerSchemaCompatibility;
import org.apache.flink.api.common.typeutils.TypeSerializerSnapshot;
import org.apache.flink.runtime.state.metainfo.StateMetaInfoSnapshot;
import org.apache.flink.util.Preconditions;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import java.util.Collections;
import java.util.Map;

/** Meta information about a priority queue state in a backend. */
public class RegisteredPriorityQueueStateBackendMetaInfo<T> extends RegisteredStateMetaInfoBase {

    @Nonnull private final StateSerializerProvider<T> elementSerializerProvider;

    public RegisteredPriorityQueueStateBackendMetaInfo(
            @Nonnull String name, @Nonnull TypeSerializer<T> elementSerializer) {

        this(name, StateSerializerProvider.fromNewRegisteredSerializer(elementSerializer));
    }

    @SuppressWarnings("unchecked")
    public RegisteredPriorityQueueStateBackendMetaInfo(StateMetaInfoSnapshot snapshot) {
        this(
                snapshot.getName(),
                StateSerializerProvider.fromPreviousSerializerSnapshot(
                        (TypeSerializerSnapshot<T>)
                                Preconditions.checkNotNull(
                                        snapshot.getTypeSerializerSnapshot(
                                                StateMetaInfoSnapshot.CommonSerializerKeys
                                                        .VALUE_SERIALIZER))));

        Preconditions.checkState(
                StateMetaInfoSnapshot.BackendStateType.PRIORITY_QUEUE
                        == snapshot.getBackendStateType());
    }

    private RegisteredPriorityQueueStateBackendMetaInfo(
            @Nonnull String name, @Nonnull StateSerializerProvider<T> elementSerializerProvider) {

        super(name);
        this.elementSerializerProvider = elementSerializerProvider;
    }

    @Nonnull
    @Override
    public StateMetaInfoSnapshot snapshot() {
        return computeSnapshot();
    }

    @Nonnull
    public TypeSerializer<T> getElementSerializer() {
        return elementSerializerProvider.currentSchemaSerializer();
    }

    @Nonnull
    public TypeSerializerSchemaCompatibility<T> updateElementSerializer(
            TypeSerializer<T> newElementSerializer) {
        return elementSerializerProvider.registerNewSerializerForRestoredState(
                newElementSerializer);
    }

    @Nullable
    public TypeSerializer<T> getPreviousElementSerializer() {
        return elementSerializerProvider.previousSchemaSerializer();
    }

    private StateMetaInfoSnapshot computeSnapshot() {
        TypeSerializer<T> elementSerializer = getElementSerializer();
        Map<String, TypeSerializer<?>> serializerMap =
                Collections.singletonMap(
                        StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER.toString(),
                        elementSerializer.duplicate());
        Map<String, TypeSerializerSnapshot<?>> serializerSnapshotMap =
                Collections.singletonMap(
                        StateMetaInfoSnapshot.CommonSerializerKeys.VALUE_SERIALIZER.toString(),
                        elementSerializer.snapshotConfiguration());

        return new StateMetaInfoSnapshot(
                name,
                StateMetaInfoSnapshot.BackendStateType.PRIORITY_QUEUE,
                Collections.emptyMap(),
                serializerSnapshotMap,
                serializerMap);
    }

    public RegisteredPriorityQueueStateBackendMetaInfo deepCopy() {
        return new RegisteredPriorityQueueStateBackendMetaInfo<>(
                name, getElementSerializer().duplicate());
    }
}
